The management and tracking of personnel, assets, and other objects is required in a wide variety of environments and is often cumbersome, labor intensive, and expensive. Radio receivers and transmitters have been used for many years to identify personnel and objects in such environments. For example, many systems are known for attaching radio tags to items, such as automobiles, so that when automobiles equipped with radio tags enter a certain area, such as a toll booth area, the automobiles are automatically identified and the appropriate tolls are deducted from corresponding accounts, thereby obviating the need for drivers to stop and make payment at toll booths. Innumerable other applications for such radio tag systems have been identified, in areas ranging from inventory control to facility security to sporting event timing.
Radio frequency identification (RFID) systems generally use a fixed position base station capable of reading remote, portable tags attached to personnel, assets, or other objects. Tags generally operate on their wake-up frequency at low frequency, very low frequency, or microwave bands. Because of power consumption concerns and the life span of the portable, remote radio tags operating at low frequency or very low frequency, exclusive OR ("XOR") gates are almost exclusively used to demodulate incoming radio frequency signals. The use of XOR gates leads to low sensitivity and limited operational range for the radio tags.